Blockchain is a type of distributed ledger used to record and verify transactions. It is a decentralised system that allows multiple parties to keep a copy of the same ledger, making it very difficult for a single party to falsify or corrupt the information stored.

A blockchain is essentially a linked list of records called blocks that contain information about transactions. Each block contains a number of transactions and a reference to the previous block in the chain, hence the name "blockchain". This creates a chain of blocks that can be thought of as a digital ledger.

The most well-known blockchain is that of Bitcoin, but there are many other types of blockchains that can be used for different purposes. Ethereum, for example, is another blockchain that is often used to create and run decentralised applications (dApps).

One of the most important features of blockchain technology is that it is based on a consensus mechanism, i.e. all parties in the network must agree on the state of the ledger. This helps to ensure the integrity of the information stored in the blockchain and makes it very difficult for a single party to manipulate the ledger.

Another important feature of the blockchain is its transparency, i.e. all parties involved can see the transactions recorded in the ledger. This transparency helps to strengthen trust in the system.

Finally, it is important to know that many blockchains use cryptography to ensure the security of the information stored. Bitcoin, for example, uses a technology called "proof-of-work" to ensure that transactions are valid and that the blockchain cannot be manipulated.

Blockchain technology has many potential applications beyond financial transactions, such as supply chain management, identity management and more.